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Frugal Living Tips - Calculating Your Power Consumption or kWh

Updated on April 26, 2012

In your quest to live a frugal lifestyle, you have no doubt realized that electricity consumption is a major component in your monthly utilities bill. You switch off the light every time you leave the room, but that doesn't seem to have too much effect. So, you are reading this article because you want to better understand the specifications of your electrical and electronics devices, so that you know how much you are actually paying for each hour of their operation.

Power Specification Of A Device

Generally, the power specification of a device will consist of its voltage rating and the wattage. It will probably look something like one of the following:

  • 240Vac 1200W
  • 240V 1200W
  • 240 Volts, 1200 Watts
  • 240V 1.2kW

If that looks like Greek to you, don't be intimidated. All you need to know now is that the specifications consist of two numbers, the operating voltage and the wattage. What you are seeing is simply different ways the manufacturer use to convey the same information.

In the example above, the voltage is 240 volts. This might be different depending on which part of the world you are in, but it is usually somewhere in the range of 100V - 160V and 200V - 260V. This figure is not used in calculating the power consumption of a device and you can safely ignore this if you are buying a device in your country meant to be used in your country.

Wattage Or Watts
The wattage of a device is the rate at which it consumes electricity. It is specified in either watts or kilowatts, where 1 kilowatt is equal to 1000 watts. Watt can be abbreviated as W while kilowatts can be abbreviated as kW.

Energy Consumption Or Kilowatt-hours
This is the amount of electricity that you consume, and this is what the power companies bill you for. Usually, it will be specified in kilowatt-hours or kWh.

Kilowatts And Kilowatt-hours
Many people who have studied electricity still get confused between kilowatts and kilowatt-hours, and in many cases, referring to the two units as if they are interchangeable. The two units are related but not interchangeable.

The wattage of a device, usually measured in watts or kilowatts, is the rate at which energy is consumed. It is not the amount of energy consumed. The energy consumed is measured in kilowatt-hours, and that is what the power company charges you for.

A good analogy can be drawn with a runner. The speed at which a runner runs is equivalent to the wattage of a device. The total distance covered by the runner is equivalent to the amount of energy or electricity used. As you can see, the speed at which a runner runs, although related to the distance that he covers, is not the same.

Calculating The Electricity Consumed
Now, let’s put it all together. To calculate the energy used or consumed, just take the wattage of the device, in kilowatts, and multiply it by the number of hours that the device is run. The result is the electricity used. Just to be complete, the formula is given below:

Energy Used (kWh) = Wattage (kW) X Hours Used (h)

Calculating The Cost Of The Electricity Consumed
Don’t worry, this is even easier than calculating the amount of electricity used. But the first thing that you will need to know is how much your power company charges for each kilowatt-hour. You can probably get the figure from your utilities bill, failing which you can always call the power company.

Once you have the charge per kilowatt-hour, just multiply the charge by the kilowatt-hour used, and you have the amount that you have spent. The formula is given below:

Amount To Be Paid ($) = Energy Used (kWh) X Charge Per Kilowatt-hour ($)

You can take the trouble to switch off the lights every time you leave the room, but if you continue to run your air conditioning throughout the night while you sleep, I’m quite sure that you would have made not much of a difference in your power bill. Knowing how much you pay to run a certain electrical device is useful in order to determine, in advance, how effective cost cutting measures will be.


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    • wandererh profile image

      David Lim 6 years ago from Singapore

      anidae - It really is that easy once you make up your mind to figure it out. If you know how to add, subtract, multiply and divide, you can calculate how much your power costs. :)

    • anidae profile image

      Anita Adams 6 years ago from Tennessee

      This is a very useful hub for me to know how much the power costs for different appliances. I am challenged in this area but you make it sound so easy.

      I voted up and useful. I look forward to reading more of your hubs. You are a good writer.

    • wandererh profile image

      David Lim 7 years ago from Singapore

      Thank you, Hello, hello,! :)

    • Hello, hello, profile image

      Hello, hello, 7 years ago from London, UK

      Super hub and very helpful

    • wandererh profile image

      David Lim 7 years ago from Singapore

      Thanks L.L. Woodard! I was thinking of doing another hub that will give actual examples and take care of "challenges" like how to convert watts to kilowatts and minutes to hours. And I have decided to go ahead with it as it seems that it does satisfy a need. :)

    • L.L. Woodard profile image

      L.L. Woodard 7 years ago from Oklahoma City

      I think the information provided is comprehensive and written in an easy-to-understand manner. I say this because I was somewhat challenged to determine power costs for various appliances, etc and now I feel I can do so with relative ease.

    • wandererh profile image

      David Lim 7 years ago from Singapore

      ecoggins - Thank you. But I'm kinda worried about the 2 formulas. I wonder if I should provide some examples of the actual calculations?

    • ecoggins profile image

      ecoggins 7 years ago from Corona, California

      I found this hub to well written and helpful. It sets forth the issue in very clear terms and helps the consumer how to understand their power consumption and how to cut their power consumption. Well done.

    • wandererh profile image

      David Lim 7 years ago from Singapore

      richtwf - Thanks! I find that it's really useful to know how much you are actually paying for each device, so that you will know where you can make the most difference in your power bill.

    • richtwf profile image

      richtwf 7 years ago

      Very useful hub which describes very simply and clearly how to calculate energy consumption and its cost. Great hub and well written!